**Fig. 4.13.** In the Hodgkin-Huxley model, the process determining the variation of potassium conductance with depolarization and repolarization with voltage clamp.

(A) Movement of n-particles as a response to sudden depolarization. Initially,

a_{n} is small and

b_{n} is large, as indicated by the thickness of the arrows. Therefore, the fraction

*n* of n-particles in the permissive state (inside the membrane) is small. Depolarization increases

a_{n} and decreases

b_{n}. Thus

*n* rises exponentially to a larger value. When four n-particles occupy the site around the channel inside the membrane, the channel opens.

(B) The response of the transfer rate coefficients

a_{n} and

b_{n} to sudden depolarization and repolarization.

(C) The response of

*n* and

*n*^{4} to a sudden depolarization and repolarization (

*G*_{K} *n*^{4} )